Two-piece center wire spark plug



Feb. 23, 1937. H. RABEzzANA Er A.

TWO-PIECE CENTER WIRE SPARK PLUG Filed Dec. 9, 1935 allya! 9: fafa E wwwwww

l.rammed Feb. z3, i931 UNITEDA STATES PATENT osi-#Ica TWO-PIECE CENTERWIRE SPARK PLUG Application December 9, 1935, Serihl No. 53,472

13 Claims.

Our invention .relates to two-piece insulated electrodes for spark plugs'of the type wherein the central'electrode is made up of an inner partwhich extends from a supporting ledge within a passage extendinglongitudinally through the insulating member of the plug, and throughwhich the electrode extends, and which ledge is located adjacent thecentral part' of said insulating member, beyond the inner end of saidmember to provide a spark gap; and a second outer part within saidpassage and extending beyond the outer exposed end of said insulatingmember. to provide a terminal for connecting a supply cable to the plug;the' upper end of said inner part being sealed gas-tight within saidpassage, and provision being made whereby a conducting path is providedbetween said electrode lparts which together form a ltwo-part insulatedelectrode of a spark plug.` The object of our invention is to securemore perfect sealing at the upper end of the lower electrode4 partwhereby leakage of gas along the electrode is more effectivelyprevented.

The drawing accompanying and forming a part of this. applicationillustrates our invention in its preferred form, and the particularfeatures wherein the same consists are particularly pointed out in theclaims at the end of this specification.

yIn the drawing:

Figure l is a view showing an insulating mem'- ber of a spark plug upona longitudinally extend- Figure 3 is a sectional view similar to Figure2l showing our invention applied to a radio spark plus.

Figures '4, 5 and 6 are fragmentary views showing our invention-modiedas to certain features thereof.`

Referring now to the drawing, the numeral 6 'K designates'a conventionalform of the insulatingmember of a spark plug, made of porcelain orequivalent ceramic material, and which member has a longitudinallyextending passage through which the central electrode of the plugextends. This e ,has a larger upper part 1 which is I l'shown asinternally threaded at 8, and a smaller lower part 9; -the passagesmerging with one another near the central part of the insulating memberwhere, anddue to the diil'erence in their diameters, an internalsupporting ledge I0 is provided.

The numeral II designates the inner oi the parts lwhich together form atwo-piece insulated electrode of a spark plug, the same tting closely 5within the passage 9 but not being cemented therein, so that said partis free to expandand contractv due totemperature variations therein andin the insulating, member. The upper end of this part has an enlargedhead I2 which rests l0 upon the ledge In as shown; and a washer of softmetal, such as copper, or of asbestos or asbestos encased in a coppersheath, may if deemed necessary be'interposed between the head I2 andthe ledge I0.

In providing a seal at the upper'end of the lower electrode part,referring particularly -to Figures 1 and 2, the part II is `put inplace, as shown in Figure l, and then a mass of plastic material I3 ofabout the consistency oi putty, 20 and shaped more or less into the formof a pellet, is dropped into the passage 1 and rests upon the head I2.This pellet is then pressed or tamped to cause it to ll the lower end ofsaid passage and form intimate contact with the interior of the lowerend thereof, andrwith and about the head I2, as indicated at Il inFigure 2. 4

The upper or outerpart I5 of the two-piece electrode, which is threadedat I6 to form an interlocking connection with the interiorly 30 threadedpart 8 of the larger passage 1, is next screwed into said passage andinto firmv engagement with the plastic material Il; which as will beappreciated now fills the interstic between the adjacent electrode partsandthe interior of 35 the passage 'l'at its lower o r inner end, and ispressed into intimate engagement with the head, I2 and the walls of thespace wherein it is con` ned. The outer end of the upper electrode partis shown as threaded, vat I1, so that a supply 40 cable may be connectedthereto.

In the application of our invention to a spark plug having means forsuppressing high frequency oscillations (which interfere with adjacentradio apparatus) as illustrated in Figure 3, 45

an equivalent pellet of plastic material is pressed ing to suppress highfrequency oscillations emai to the spark plug.

The plastic material is madefrom a liquid binder in which an inertingredient is incorporated to impart consistency thereto, said binderbeing characterized in that when heated it will harden and become solidwithout access'of air thereto, and without the liberation of gas orvolatile products as an incident to such hardening process due, as weunderstand, to decomposition of the binding material itself or of aningredient thereof. The inert material has nothing to do with thehardening, when heated, of the liquid constituent of `the plastic mass,its use being as a filler to impart consistency to the mass so thatitmay be shaped into pellet or like form and distorted to fill the spacewherein it is contained, as above explained. The insulating member 6with the electrode parts assembled therewith, as in Figure 2, or withvthe inner electrode part' sealed in place as in Figure 3, may be heatedto accomplish the hardening and solidication of the binder before theinsulated member is assembled with the shell or casing of a spark plug;or the completed plug may be put into use before the binder has hardenedto form a solid mass, in which case such hardening will occur as soon asthe plug becomes heated when it is in'use with an engine. The plasticmaterial I4 as a. matter of course provides a gas-tight seal.

before it is subjected to the heating step; but setting and hardening ofthe liquid binder and conversion of the plastic mass into a solidsealing member whereby it becomes in effect a part of the insulatingmember itself, is dependent upon heating and does not occur untilthesame is heated; either initially and before the insulator and electrodeparts are assembled within a spark plug casing, or after the plug hasbeen finished and during the initial period of its use with an engine.

The hardening when subjected to heat, without the liberation of vaporsor gases, of the liquid binding ingredient of the sealing material, is aproperty or characteristic of certain vegetable oils and is commonlyreferred to as polymerization of such oils. This property is especiallypronounced in tung or China-wood oil, and that is the binding materialwith which we have secured the best results in providing a seal inaccordance with our invention; as a mass of plastic material made up ofsuch a binding material and an inert filling material will, when heated,harden and form a dense mass which adheres tenaciously to the wall ofthe space or chamber wherein it is connedand secure gas tightness at theseal; the hardening and solidication of the mass being accompanied by noliberation of gaseous products within said space.

We have also secured successful sealing in accordance with our inventionusing perilla oil, linseed oil, rapeseed oil, and similar vegetablevoils of the class commonly referred to as drying oils, as liquid bindingmaterials, which oils are supposed to dry and harden mainly if notwholly by absorbing oxygen from the surrounding atmosphere, rather thanby the effect of heat and without access of air tov them. 'Iheselast-named oils, however, contain ingredients which interfere with thehardening when heated, and without the liberation of a gas or vapor, ofa plastic mass whereof they comprise the liquid binding material; butwehave secured satisfactory results .(using such oils as liquid bindingmaterials), by adding sulphur monochloride to them to the exv tent ofabout of the amount of the oil used; so that such oils when so treatedmay be used in place of tung or China-wood oilwhich requires no addedingredient to adapt it for use in performing our invention.

The inert materials mixed with the binding oils may be of various kinds,as they act as fillers and do not enter into the setting and hardeningprocess of the plastic mass under the influence of heat as hereinbeioreexplained; and we have used talc, French chalk, litharge, clay,lampblack, granular graphite, copper and other metals in powdered formas inert materials with success; although we regard tung or China-woodoil and graphite as the best composition to use for the sealingmaterial. black, graphite, granular copper, etc. are used, the sealformed is conductive of electricity to various degrees, and suchmaterials are recommended in the forms of our invention illustrated inFigures 2 and 3; whereas when the other materials enumerated or theirequivalents are used our invention is usually modified as illustrated inFigures 4, 5 and 6 to be hereinafter described.

It follows that'the electrical resistance of the sealing material variesthroughout a wide range. If a powdered metal, or graphite, or iflampblack is used as a filler, then the resistance of an electrode,including that of the sealing material, of the form shown in Figures 2and 3 will not be high 'enough to be objectionable; and in all cases andeven though the resistance at the seal maybe higher than is desirablethe initial llow of high tension current will ionize the sealingmaterial and establish a conducting path of comparativly low resistancewhich will persist during the subsequent operation of the plug.

When, however, the sealing material after being heated to secure thehardening thereof may be of greaterv resistance, electrically, than isdesirable, a conducting path may be provided between the lower and upperparts of the two-part electrode. Thus Figure 4 shows the upper electrodepart 22 as having a pong 23 at lts inner end; and when such a form ofupper electrode part is screwed into the threaded passage 1 in th'einsulating member said prong pierces the plastic sealing mass 24 and itsextremity engages the head I2 and is curled over as shown, thusestablishing a metallic conducting path between the parts 22 and II ofthe central electrode. As an obvious variation the lower electrode partmay have a prong 25 upon its head, as shown in Figure 5, in which casethe lower end of the upper part I5 engages the extremity thereof andcurls it over as shown. `In either case theprong yields until theplastic sealing material is forced into intimate contact with the innerwall of the space wherein it is enclosed, thus securing gas tightnessand at the same time establishing a conducting path between adjacentends of the twopiece central electrode.

The prong is preferably provided upon the upper one of the electrodeparts, as in Figure 4, because it is ordinarily made of a softer andmore easily machined material, and of a cheaper material than the lowerpart; and because the plastic material pellet I3 may be more readilycompressed and tamped within the lower end of the passage I and aboutthe head I2 if said head has no projection like the prong 25 extendingyupward therefrom.

'I'he projection or pro'xg may, however, be cylindrical in form as shownat26 in Figure 6 wherein it extends from the upper end of the When suchmaterials as lampy lower electrode part 21, and is surrounded by sealingmaterial 28; this form, being preferable when a high resistance elementi9 is incorporated in the plug structure to prevent the ignition circuitfrom interfering with adjacent radio apparatus, as in so-called radiospark plugs; as in such cases the upper end of the projection provideseaconvenientsupportiorthehighresistance member. Such a projection,however, may be used in the forms of our invention illustrated inFigures 4 and 5 in which case 'the'lower electrode part is pressed' andheld against the seat l with more force during the assembling of theparts within the passage in the insulating member, and is more securelyheld in place because oi the greater. area yof contact provided by thecylindrical as distinguished from the conical projection, than whenlthe/tapered and yieldable pointed form of prong is used. 'I'he sealingmaterial I8 in Figure 3 has enough graphite or granular metal in itscomposition to make it a suiliciently good conductor; and theprojection, whether conical or cylindrical in form, may extend fromeither the uppei` or the lower of the electrode parts as illustrated inFigures 4 and 5. I

In order to bringr about setting and solidifiy cation of the plasticsealing mixture whereby sealing of the central electrode is accomplishedthe same is heated to a temperature around 250 C. ior a period oi'aboutten minutes; during which the plastic composition sets and hardens withan l,accompanying slight expansion, thus securing. complete and certaingas tightness in the completed plug. 'I'his heating as explained ispreferablyl of the insulating member after the central electrode hasbeen assembled therewith, and before the member has been assembledwithin the shell of a spark plug; but and as explained the plug may beyirst completely assembled, whereupon and during a short initial periodof -use complete setting of the plastic mixture will take place.

Having thus described and explained our invention, we claim and desireto secure by Letters Patent:

1. In combination with a spark plug insulator having a passageextending'therethrough for a central electrode; a two-piececelectrodeextending` through, and adjacent ends of the two parts of which liewithin said passage and are spaced apart from one another; and a plasticsealing member lling they space between said two ends; said membercomprising a liquid vegetable drying oil binder which will harden andbecome solid when heated, and an-inert material incorporated with saidbinder.

2. In combination with a spark plug insulator having a passage extendingtherethrough for a central electrode; a two-piece electrode extendingthrough, and adjacent ends oi.' the two parts of -which lie within saidpassage and are spaced apart from one another; and a plastic sealingmember filling the space between said two ends; said member comprising avegetable oil binder which when heated will polymerize and form a solidmass, and an inert material incorporated with said vegetable oil binder.

3. In combination with aspark plug insulator having a passage extendingtherethrough for a central electrode; a two-piece electrode extendingthrough, and adjacent ends of the two parts of which lie withinsaid'passage and are spaced apart from one another; and a hardened sealv6 ing member filling the space between said two 7 ends and formed byheating a mass oi plastic material made up of a polymerizing vegetableoil and an inert lling material.'

4. In combination with a spark plug insulator having av passageextending therethrough for a central electrode; a two-.piece electrodeextending through, and adjacent ends of the two parts' of which liewithin said passage and are spaced apart from one another; and ahardened sealing member filling the space between said two ends andformed by heating a mass of plastic material made up of a polymerlzingvegetable oil mixed with an inert filling material having electricityconducting properties. I

5. In combination with a spark plug insulator having a passage extendingtherethrough for a central electrode; a two-piece electrode extendingthrough, and adjacent ends oi the parts of which lie within said passageand are spaced apart from one another; and a sealinglmember illling thespace between said two ends; said member comprising a tung or China-woodoil binder and an inert iilling material incorporated therewith and`hardened by applying heat thereto.

6. In combination with a spark plug insulator having a passage extendingtherethrough for a central electrode; a two-piece electrode extendingthrough, and adjacent ends of the parts of which lie within said passageand are spaced apart from one another; and a sealing member filling thespace between said two ends; said member being composed of a tung orChina-wood oil binder and powdered graphite mixed together and hardenedby heating said member.

7. In combination with a spark plug insulator having a passage extendingtherethrough for a central electrode; a two-piece electrode extendingthrough, and adjacent ends of the two parts of which lie within saidpassage; and a plastic sealing member lling the space between said twoends; one of the parts of said electrode having a projection whichextends .through said plastic sealing member and contacts with the otherof said electrode parts to establish a conducting path between saidparts.

8. In combination with a spark plug insulator having a passage extendingtherethrough for a central electrode; a two-piece electrode extendingthrough, and adjacent ends of the two parts of which lie within saidpassage; and a sealing member filling the space 'between said two endsand formed by heating a plastic mass comprising a polymerizing oil mixedwith an inert iilling material, to thereby harden said mass; one of theparts of said electrode having a projection which extends through saidsealing member and contacts with the other of said electrode parts toestablish a conducting path between said parts.

9. In combination with a spark plug insulator having a passage extendingtherethrough for a central electrode and a supporting ledge within saidpassage; an inner electrode part having an enlarged head which restsupon said ledge; and a plastic sealing member within said passagewh'ereby a gas-tight seal is provided adjacent said head; said sealingmember comprising a vegetable oil binder which when heated willpolymerize and form a solid mass, and an inert material incorporatedwith said vegetable oil binder.

11. In combination with a spark plug insulator having a. passageextending therethrough for a central electrode, and a supporting ledgewithin said passage; an inner electrode part having an enlarged headwhich rests upon said ledge; and a hardened sealing member within xsaidpassage Whereby a gas-tight seal is provided adjacent said head; saidsealing member being formed by heating a mass of plastic material madeup of a polymerizing vegetable oil and an inert filling material.

12. In combination with a spark plug insulator having a passageextending therethrough for a central electrode; a central electrodeextending" through said passage; and a sealing material associated withsaid electrode and acting to pre-` vent the flow of gas along saidpassage; said sealing material comprising a vegetable oil binder whichwhen heated will polymerize and form a solid mass, and an inert materialincorporated with said vegetable oil binder. X

13. In combination with a spark plug insulator having a passageextending therethrough for a centralV electrode; a central electrodeextending through said passage; and a sealing material associated withsaid electrode and acting to prevent the flow ofY gas along saidpassage; said sealing material being located at the central part of saidelectrode, and the same comprising tung or China-Wood oil mixed with aninert filling material.

HECTOR RABEZZANA.

TAINE G. McDOUGAL.

JAY T. FORD.

WILLIAM S. KIRK.

